This invention relates to electrical insulators of the kind having a central portion with one or more sheds extending outwardly therefrom.
Insulators for high voltages in power supply systems commonly comprise a stem or a body of cylindrical or truncated conical form with sheds extending outwardly therefrom, the sheds being spaced along the length of the stem. Such insulators are most commonly made of porcelain although other materials may be used, for example epoxy resins. Particularly in use in the open air, pollution collects on such insulators leading to the occurrence of electrical discharges over the surface of the insulator. The present invention is directed to hindering the propagation of such electrical discharges and thereby increasing the ability of the insulators to avoid flashover.
It is well known to provide means for washing insulators particularly under conditions where they are exposed to possible heavy pollution, as for example near a sea coast where salt may be deposited on the insulators. Such washing is effected by means of high pressure water jets or sprays and will remove the pollution layer from the surface of the insulator. During such washing and just after washing when water with a high pollution content is running down the insulator, there is a high risk of flashover occurring and the present invention finds particular application for such insulators having washing facilities.